Pendulum GPS-12, Руководство пользователя

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short distances between antenna and receiver. It
is more flexible, however, and might be utilized
with care, if you are fully aware of its charac-
teristics.
Remaining parameters to consider are:
Antenna gain:
Guard band:
Total external gain at
the receiver input: +36 dB (option 01)
±3 dB
+11dB … +33 dB
When designing your own antenna installation,
you must check that the gain at the receiver in-
put is within limits according to the above ta-
ble. That is, you must check that:
+ antenna gain
- total attenuation
+ total amplification
- guard band + antenna gain
- total attenuation
+ total amplification
+ guard band
³
+11 dB
£
+33 dB
n
Case Classification
The distance between antenna and
receiver exceeds 20 m but not 55 m
–
Use a coaxial cable of type RG-213 or
cascade two or three pieces of option 02
by means of adapters. Note that normal
adapters are not weatherproof and should
be placed indoors. Normally there is little
to gain by using a low-loss cable in this
case, but see example #1 below. RG-213 is
more inexpensive and flexible.
The distance between antenna and
receiver exceeds 55 m but not 130 m
–
Use a low-loss coaxial cable of type LMR
400 or equivalent.
The distance between antenna and
receiver exceeds 130 m but not 245 m
–
Use a line amplifier with a nominal gain
of 20 dB plus low-loss coaxial cable of
type LMR 400 or equivalent. The ampli-
fier must accept a fixed +5 V supply volt-
age fed through the central conductor of
the coaxial cable. The maximum input
power for linear operation should be at
least –6 dBm, and the noise figure should
be less than 2 dB.
The distance between antenna and
receiver is in the range 245-360 m
–
Use two cascaded line amplifiers (20 dB
each) plus low-loss coaxial cable of type
LMR 400 or equivalent.
Better protection against lightning
strikes needed
Lightning protection is a wide field and cannot
be covered more than superficially in this man-
ual. If the building is situated in a risk area, a
general survey of the overall house protection
might be needed. Especially lightning rods near
the GPS antenna mounting mast should be in-
spected. Make sure that the antenna is far from
being the highest point and, as a precaution,
ground the mounting mast as if it were part of
the ordinary lightning rod system.
There are several conditions that may call for a
separate lightning arrester to support the
built-in antenna protection.
–
The cable length outside the building ex-
ceeds
15 m.
–
An elevated antenna position with no effi-
cient lightning rods nearby.
–
Areas where the frequency of thunder-
storms is significantly higher than normal.
8-4 Antenna Installation
Appendix